The collectives that have been spawned in the past few years in the San Francisco area offer a wide assortment of antiques and collectibles under one roof and at reasonable prices. Most of them are providing at least part-time occupation and some ready cash for housewives, couples, and young singles who enjoy collecting for resale, but want to do it in their own good time and minus the cares of shop ownership.

The Collectors' Market, on e of a dozen or more midpeninsula collectives, is a good example of this new method of buying and selling goods. It consists of 7 ,200 square feet of wide open space with a storefront, which Barbara Pfieffer and Sandy Baisa, both wives with some time to spare, leased three years ago, thinking that "it would be fun just to do our own thing and manage a collective."

They divided the area into 10-by-12-foot spaces, which they rent for $220 a month to 32 collector-dealers who want to reach the public with their overflow. Mrs. Pfieffer and Mrs. Baisa also collect an 8 percent commission on all sales made at their Collectors' Market for building maintenance and security, and all other overhead expenses which include the services of a full-time manager and assistant manager as well as advertising and bookkeeping costs.

Each of the 32 dealers has to volunteer one day of service a month to the collective, but is otherwise free to come and go at will. The dealers simply keep their spaces stocked. Customers who come to browse and buy more from space to space, and, as in any supermarket, pay for the objects they wish to buy at a central checkout counter. Sales are credited there to the individual exhibitors whose goods are involved.

The day of my recent visit I not only found an incredible amount of items for sale, but stopped for a visit with Laurie Goben and Dolores Degnan, two housewives who call their booth The Gray Goose and say it is a combined hobby and business.

"We both love tackling estate, yard, and tag sales, as well as flea markets, swap meets, charity bazaars, auctions, and any other sales event that offers old and secondhand things," Laurie explains. "We just think of ourselves as being on a perpetual treasure hunt, and when we find something super, it's great thrill."

At that moment a girl customer was trying on, with apparent delight, an array of 1930s and '40s sailor and cloche hats in front of a 1930s dresser mirror. Another browser was looking at old green glass juicers, green-handled can openers, crocks, old graters, and toasters.

"Old kitchen things are big right now," Laurie comments, "and so is 1930s furniture. Although actually we have found that almost anything that is interesting, old, and well-made sells.

"The hazard in this business is in not being able to part with one's discovered treasures," Laurie goes on. "I always ask myself 'Who would appreciate it more than me?' So my home is now dense with things that I love and that nobody could appreciate more than me. Fortunately, if things get too cluttered or if i get tired of something, I can always sell it." Although there is a quick turnover of stock, I strolled, along with a lot of other buffs and aficionados of the secondhand, past practical Hoosier cabinets, old sewing machines and wall telephones, hall trees, whatnots, umbrella stands, school desks, old iron beds, rolltop desks, and antique wash stands.

Nothing is sold "as is;" each item has been cleaned up, repainted, or refinished so customers can take it home and enjoy it at once.

"People, and newlyweds especially, are always looking for practical furnishings such as dining tables and chairs and chests. They usually prefer them in solid pine or oak," explained Mrs. Baisa, one of the owners. "Many people come here to buy wedding and anniversary gifts. Many are looking these days, too, for old photographs, old lace and linens, glass of all kinds, and old Victrolas, pump organs, and juke boxes."

This particular collective for the sale of antiques and collectibles is open seven days a week.